1. Technical Field
The present disclosure relates to a turbocompressor apparatus.
2. Description of the Related Art
Various proposals have been made regarding a system using a compressor and motor control. For example, Japanese Patent No. 5575379 (hereinafter referred to as Patent Literature 1) describes a freezing machine 900 illustrated in FIG. 12. The freezing machine 900 includes a compressor 901, an evaporator 902, a condenser 904, a cooling column 916, and a cooling water pump 918. In the freezing machine 900, water is used as a cooling medium. The compressor 901 has a rotary shaft 910, an impeller 912, and a shaft bearing 920. Water is fed from the cooling column 916 to the condenser 904 and fed from the cooling column 916 to the shaft bearing 920 by discharge pressure of the cooling water pump 918. The water fed to the shaft bearing 920 acts as a lubricant. Japanese Unexamined Patent Application Publication No. 2015-126598 (hereinafter referred to as Patent Literature 2) and Yuichiro MAEDA, Yukinori INOUE, Shigeo MORIMOTO, Masayuki SANADA, “Operating Characteristics of Direct Torque Control System for Interior Permanent Magnet Synchronous Motors in Overmodulation Region”, 2012 IEE-Japan Industry Applications Society Conference, Vol. 3, pp. 243-246 (2012-8) (hereinafter referred to as Non-Patent Literature 1) describe motor control.
Because of contact between a rotary shaft and a shaft bearing of a compressor, there is a possibility of wear of the rotary shaft or the shaft bearing. The technique described in Patent Literature 1 has a room for improvement from the perspective of a reduction of wear. The present disclosure was accomplished in view of such circumstances.